In the processing of substrates, such as semiconducting wafers, a substrate is placed on a substrate support in a process chamber. In process chambers, process kits are utilized to prevent undesired deposition on one or more chamber components. The support for the wafer is often a support member such as an electrostatic chuck, to hold the substrate in proper position during the processes performed. Typically, a substrate, or wafer, is placed on the support member by an automated robot. The substrate must generally be centered with the electrostatic chuck in order for the substrate to be processed uniformly, thus the automated robot places the substrate in a rough location initially, and then the location is accurately determined by a few well known methods.
The most common method for substrate placement is to view the substrate under a clear window and adjust placement based on how well the substrate is centered to the process kit surrounding the substrate. However, this method has limited accuracy because the process kit may not be well centered with respect to the support member. Other methods involve relying on etch rate or uniformity of substrates that have already been etched. These methods can be more accurate than the previous method, but can take several hours to get data for adjustment of substrate placement. A third method is to transfer the pattern of the support member onto a substrate either by transferring particles or physically damaging the substrate. While the particle method is accurate, pattern transfer can be unreliable and features on the support member can vary slightly in location, thus resulting in incorrect placement of the substrate.
Accordingly, the inventors have provided embodiments of improved methods and apparatus for determining substrate placement in a process chamber.